1. Field of the Invention
The present invention relates to tolerance indicating trim marks for printed sheets containing machine readable indicia.
2. Description of the Prior Art
Automatic test scoring devices are widely used to score test sheets on which answers have been marked in designated true/false or multiple choice answer spaces. An example of such device and of the test sheets used thereby is disclosed in the inventor's U.S. Pat. No. 3,800,439 entitled TEST SCORING APPARATUS. In such devices, answer marks are detected electro-optically as each test sheet is transported past a photo-electric reading head.
For error-free operation, the answer spaces on each test sheet must be spaced certain distances from a reference edge of the sheet. These distances correspond to the positions of photosensors in the reading head with respect to a guide for the test sheet reference edge. Typically the answer spaces are arranged in columns parallel to the reference edge, with the answer blocks in each column being a fixed distance from the reference edge.
If the reference edge is skewed with respect to the columns of answer spaces, not all of the spaces will be aligned with the corresponding sensors as the sheet is transported past the read head. Incorrect scoring will result.
To avoid this problem, the answer spaces are printed on a page together with a trim line defining the reference edge. The page subsequently is severed along the trim line, so that in the resultant answer sheet the answer spaces are exactly spaced the desired distance from the reference edge. Two answer sheets may be printed simultaneously on the same page, so that the single trim line defines the reference edges for both test sheets.
Some tolerance is permitted in the position of the reference edge with respect to the answer spaces. To inform the printer that the pages have been severed within this acceptable range, tolerance indicating trim marks advantageously are printed on the page along the trim line.
An example of such trim marks is disclosed in the U.S. Pat. No. 3,808,406. There each mark consists of a generally rectangular tolerance indicating portion and a coaxial line portion extending from the ends thereof. The line portion designates the exact trim line, and the transverse dimension of the tolerance indicating portion corresponds to the allowable trim tolerance. If the page is severed within acceptable limits, a solid band of ink is visible down the edge of a stack of sheets. Absence of this band indicates that the sheets have been cut improperly and must be discarded.
It is an object of the present invention to provide improved trim marks for a test sheet. These trim marks not only indicate whether the pages have been severed within acceptable tolerance, but also tell exactly how far from the trim line the actual cut has been made. Moreover, the inventive trim marks also indicate at a glance whether and in which direction the cut edge is skewed.
Although intended primarily for test answer sheets, the trim marks disclosed herein have other applications. For example, in the printing of bank checks which contain machine readable bank transit and account numbers along one edge, that edge must be exactly spaced from the bottom of the numbers. The inventive trim marks may be used to define the trim line and acceptable tolerance for trimming such bank checks.